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Explained: Nipah virus in the time of Covid-19

A boy infected with the Nipah virus has died in Kerala, a state already hit badly by Covid-19. How do the two viruses compare in transmissibility and fatality? How is Kerala addressing the twin concerns?

Kerala Nipah virus, Nipah virus, What is Nipah virus, Nipah virus symptoms, Nipah virus treatment, Kerala news, Indian ExpressA central team of experts visits homes at Chathamangalam in Kozhikode, where the Nipah victim haiiled from, on Sunday . (Express photo)

A 12-year-old boy infected with the Nipah virus died in a private hospital in Kozhikode on Sunday morning. The boy showed symptoms of encephalitis and myocarditis – inflammation of the brain and heart muscles respectively.

The re-emergence of the Nipah virus in Kerala poses a fresh risk in the state that is already struggling with the Covid-19 pandemic, contributing about 60% of all new cases in the country these days. However, this is not the first time that Nipah virus has been detected in Kerala, or elsewhere in India, and previous outbreaks have remained largely localised and have been contained relatively quickly.

What is the Nipah virus?

The first outbreaks of the Nipah virus among humans was reported from Malaysia (1998) and Singapore (1999). The virus takes its name from the village in Malaysia where the person in whom the virus was first isolated died of the disease.

Since it was first identified in 1998-99, there have been multiple outbreaks of the Nipah virus, all of them in South and Southeast Asian nations. In Bangladesh, there have been at least 10 outbreaks since 2001.

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In India, West Bengal had seen an outbreak in 2001 and 2007, while Kerala had reported several cases in 2018.

How does Nipah virus spread?

It is a zoonotic virus, meaning it has been transmitted from animals to human beings. The transmission happens mainly through consumption of contaminated food. But human-to-human transmission is also considered possible. The animal host reservoir for this virus is known to be the fruit bat, commonly known as flying fox. Fruit bats are known to transmit this virus to other animals like pigs, and also dogs, cats, goats, horses and sheep.

Humans get infected mainly through direct contact with these animals, or through consumption of food contaminated by saliva or urine of these infected animals. Person-to-person transmission is not fully established, but a recent study, published by two Bangladeshi researchers in March this year, said that previous outbreaks in Bangladesh, the Philippines and India suggested “that respiratory droplets of an infected person can transmit the virus”. During previous outbreaks, people in close contact with the infected person, mainly hospital staff and caregivers, have contracted the disease.


Does Nipah spread as fast as Covid-19?

The Nipah virus is known to spread far more slowly than SARS-CoV-2. However, it is its ability to kill that is the biggest concern. During the first outbreak in Siliguri, 45 of the 66 people confirmed to have been infected died. That is a mortality rate of 68%. In the next outbreak, in Nadia district of West Bengal, in 2007, all the five infected people died.

During the most recent outbreak in Kerala in 2018, 17 of the 18 patients confirmed to have been infected died. In 2019, one case of Nipah virus infection was detected in Ernakulam, but prompt response restricted any further spread. The infected person survived.

In the Malaysian outbreak in 1999, a total of 265 people had been found infected, of whom 105 had died, according to a study, ‘Nipah Virus: Past Outbreaks and Future Containment’, by researchers from Cochin University of Science and Technology published in the April 2020 issue of the journal Viruses.


In comparison, the mortality rate of Covid-19 epidemic is expected to be around one per cent.

Kerala Nipah virus, Nipah virus, What is Nipah virus, Nipah virus symptoms, Nipah virus treatment, Kerala news, Indian Express Human beings can get infected if they come in close contact with the infected animal — bats or other animals such as pigs — or its body fluids such as saliva or urine. (Express Photo: Javed Raja, File)

How well has Kerala handled previous Nipah outbreaks?

In 2018, Kerala had no past experience of handling a disease with such a high fatality rate. The state followed the protocol for Ebola virus disease which had been reported mainly in sub-Saharan Africa.

At one point in June 2018, around 3,000 people were under quarantine in Kozhikode and nearby Malappuram districts. All the persons who had direct or indirect contact with the suspected Nipah cases were thus put under observation.

When the state reported Nipah again in 2019, the health department already had a protocol in place to handle the situation. In 2019, only one case was reported in Ernakulam district.

In 2020, the state did not report any Nipah case, but the protocol was updated and sent across the system.


How is Kerala handling the fresh Nipah concerns alongside Covid-19?

The Nipah virus victim hailed from the village of Chathamangalam, 50 km from Changaroth. Three wards under Chathamangalam panchayat in Kozhikode, where the victim lived, were completely closed down on Sunday morning. Micro-level restrictions have gone into effect.

Movement to and from these three wards have been banned. Police have put up barricades and checkpoints at all locations leading to the village of the victim.


With Covid-19 protocols already in place, there is heightened awareness about transmission of viral diseases. The ongoing use of PPE kits, gloves and masks, especially by healthcare workers and hospital staff, is likely to offer reduced opportunity for the transmission of the Nipah virus.

Should other states worry about Nipah spreading?

Thus far, all outbreaks of the Nipah virus have been localised and contained quickly, at least in comparison to the ongoing Covid-19 pandemic. The first outbreak in Malaysia started in September 1998, although it was only by March next year that scientists were able to confirm that this was a new virus they were dealing with. The outbreak was contained by May. In Bangladesh, where Nipah outbreaks have been the most recurrent, the transmissions have stopped after a couple of months.


One of the main reasons for a relatively quick end to an outbreak is the fact that Nipah virus is far less infective than SARS-CoV-2, for example. Human-to-human transmission is not as easy, or as fast, as seen in the case of SARS-CoV-2.

A study by Bangladeshi researchers P Devnath of Noakhali Science and Technology University and H M A A Masud of Chittagong University, published this year, noted that the reproductive number (R0) in the previous outbreaks of Nipah virus was about 0.48. The R-value is a measure of how quickly the virus spreads in the population. A value less than one means less than one person is being infected by an already infected person. In such a scenario, the outbreak is expected to diminish relatively quickly.

The study also notes that since Nipah outbreaks have happened mainly in sparsely populated villages, the potential of the virus to spread to many individuals has been low. Further, the very high death rates also contribute to low transmission.

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First published on: 06-09-2021 at 03:45:36 am
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